Method of sewing textile webs together



Feb. 8, 1966 D. w. GARDNER 3,234,061

METHOD OF SEWING TEXTILE WEBS TOGETHER Filed Jan. 24, 1965 Textile web having a transverse but? seem free from roused porrions,sewn Min 0 bicomponent thread cdhesively secured to the faces of the web by a ihermoplasiic component of the thread INVENTOR.

ATTORNEY tent fiice 3,234,6lfil Patented Feb. 8, 1966 3,234,061 METHOD OF SEWZNG TEXTELE WESS TOGETHER Donaid W. Gardner, Pendleton, S.C., assignor to Deering Miiliken Research Corporation, Spartanhurg, S.C., a corporation of Delaware Filed Jan. 24, 1963, Scr. No. 253,592 13 Claims. (Cl. 156-93) This invention relates to a method of joining together ends of lengths of textile webs and, more particularly to a method involving sewing the ends together and then heat.- ing the seam area to produce a seam which will not interfere with subsequent treatment of the web, and to textile webs thus joined.

In certain treatments of textile webs, it is often undesirable to have a transverse seam in a running length of in the shearing operation, as much as a quarter of a yard or more of the fabric is not sheared at the area of the seam and thus becomes waste fabric. Such a loss of fabric constitutes a considerable expense to the mill over a period of time.

Also, in the laminating and coating trade, where textile webs are subjected to high pressure calendering operations, a transverse seam having raised threads presents serious problems. If such a seam is present in the web, the pressure on the calender or laminating rolls ordinarily must be released momentarily and up to several yards of fabric are thus not properly calendered or laminated, because of the speed of laminating and ealendering operations. Even if the seam is not raised sufliciently to require releasing the pressure from the pressure rolls, any raised portions at the seam will produce a visible defect in the surface of the coated fabric and thus produce a second, which must be sold at a lower price. Consequently, laminators and coaters sometimes refuse to purchase short lengths of fabric joined by a conventional transverse seam.

It is possible to overcome some of these objections by covering the seam with an adhesive tape which covers the exposed portions of the sewing thread. However, the thinnest tape available provides a seam still too thick to eliminate allof the problems described above. Also, the use of tape is troublesome and time consuming.

It is therefore an object of this invention to provide a method of joining together ends of textile webs so as to provide a seam substantially free from raised portions without the presence of adhesive material in excess of that required to produce this scam.

It is another object to provide a method of joining the ends of textile webs together so as to provide a seam which does not interfere with subsequent mechanical and/or chemical treatments of the textile web.

It is still another object to provide lengths of fabric having novel seams therein.

Other objects will be apparent to those skilled in the art to which this invention pertains.

According to this invention, lengths of textile webs are joined together by sewing to form a transverse butt seam with thread consist-ing essentially of at least 60% of a fibrous supporting component which neither flows nor substantially degrades when heated up to 225 C. for a short period of time and at least 10% of a thermoplastic non-fibrous component which flows when heated. The seam is then heated under pressure so that the non-fibrous component ilows into the web and the fibrous component is pressed tightly into the face of the web, thereby causing the exposed portions of the thread to be firmly and adhesively bonded to the face of the web. The heat and pressure are then removed, thus producing a seam substantially free from portions raised above the faces of the web.

The advantages of this novel process will be immediately apparent to those skilled in the art.- This process now permits joining of the ends of textile webs by conventional sewing procedures and only a heating unit to which pressure can be applied is required to produce the desirable fiat seam. It was surprising to find that as little as 1%, calculated on the weight of the thread, of the nonfibrous component is necessary to achieve the desired results. It will be apparent that the exact minimum amount which can be employed in any particular situation will depend upon the adhesiveness of the selected nonfibrous component to the selected web. The use of such small amounts which, on the weight of the fabric, is much less than is employed as bonding material when a conventional seam is covered with tape, substantially elimihates the possibility of any build-up of the thermoplastic material in the heating apparatus used to produce the bonded seam or in any subsequent operation in which the seamed web is brought in contact with a heated surface. Also, the bonding of the seam can be completed in a very short time, which is especially desirable in such an operation.

This invention is illustrated in the accompanying drawings in which- FIG. 1 is a schematic view of a portion of a textile web 1 having a transverse butt seam 2 therein formed with sewing thread 3 following this invention, and

FIG. 2 is a highly enlarged schematic cross-view scetional view along line IIII of a woven fabric containing a transverse butt seam of the type shown in FIG. 1.

As shown in FIG. 2, the woven fabric 1, formed in the conventional manner from a multiplicity of warp ends 4 and filling ends 5 is butt seamed with a bicomponcnt sewing thread 6 containing a thermoplastic non-fibrous component 7 which bonds the thread 6 tightly to the faces of the fabric 1. As FIG. 2 shows, the exposed portions of the thread 6 are pressed tightly into the face of the fabric by pressure which flattens the fabric threads 4a and 5a in the seam area as well as the exposed portions of the sewing thread so that the seam area is at the same height as or even below the level of the faces of the fabric.

Textile webs which can be seamed according to the process of this invention include the woven, knitted and nonwoven fabrics. These fabrics can be formed of natural cellulosic materials, e.g., cotton, synthetic cellulosic material, e.'g'. unmodified and polynosic rayons, and wool. Ordinarily, the process will be directed to fabrics consisting entirely of non-thermoplastic materials.- However, with the proper selection of the thermoplastic compon'entin the sewing thread used in the process of this invention, the fabrics can consist partially or wholly of the synthetic thermoplastic materials, e.g., ethylene glycol terephthalate polyesters, the nylons, and the polyacrylics. The preferred webs employed in the process of this invention are the woven cotton, rayon and wool fabrics, particularly the latter where the savings in fabric by following the present process is highly significant.

The sewing thread used in the process of this invention contains from 1% to 40% of a thermoplastic non-fibrous component and from 99% to 60% of a fibrous supporting component, both as defined hereinafter, preferably at least 3% of the former and more preferably between about 3% and 30% of the former. While the sewing thread will often include other materials, e.g., lubricants, waxes,

softeners, sizing materials, etc. As with all sewing threads, the thread should be formed of such materials and so constructed as to have suflicient strength to withstand the sewing tensions and also so as to have substantial residual strength after the thermoplastic component has flowed in the heating operation so that the seam will not part when the textile web is subjected to the conventional processing tensions.

The thermoplastic non-fibrous component is present in the form of a coating on the fibrous supporting component, e.g., as a substantially external coating on the thread or It can be in more intimate. association with the supporting component by being distributed around the individual fibers of the supporting component.

The fibrous supporting component can be any of those materials conventionally employed in sewing threads, e.g., ordinary and mercerized cotton and regular and partially cross-linked rayon. It can be in filament, multifilament or staple form. While the supporting component ordinarily will be non-thermoplastic, thermoplastic materials, e.g., nylons and polyesters, can be used if the coating material has a substantially lower flow temperature. Fibrous as used herein means oriented materials in the textile sense as opposed to coatings and other unoriented materials.

The thermoplastic coating component of the abovedcscribed sewing thread is one having a Vicat flow temperature (A.S.T.M. D569-59, procedure A), between about 100 and 225 C., which is below the temperature at which the web on which the seam is to be formed substantially degrades when heated for a short period, i.e., about one minute or less. Such materials include the non-fibrous forms of plasticized, partially polymerized phenol-formaldehyde resins, polyurethanes, the polyvinyl acetates, polyvinyl butyrates, polyvinyl chlorides, the acrylic monomers and methacrylic polymers and mixtures thereof. Thermoplastic fibrous materials which become thermosetting upon heating can also be used, e.g., the aminoplasts and the phcnoplasts. Such materials are suitably employed where the textile web is subsequently subjected to a heating operation which would adversely affect a seam bonded with a non-thermosetting material. However, in practice it has been found that the web containing the scam can be subjected to an operation such as a decating or rotary press operation which heats the fabric at least momentarily to temperatures above the flow temperature of the thermoplastic component without ad vcrsely affecting the resultant seam or the equipment. The selected thermoplastic material should provide a relatively tack-free condition at room temperature to the thread, at least after the application of suitable anti-tack material to the thread, so that the yarn can be sewn using conventional techniques.

To improve flexibility, the conventional softeners and/ or plasticizers preferably are incorporated in the bicomponent thread. Materials such as penetrating oils, light oils, silicones, etc. are useful in this respect. Such lubricants are important to provide a thread which is flexible enough to be used in industrial sewing machines. As a .2 coating operation tends to rigidity the thread, because of the bonding effect in the threads or the individual fibers, means such as lubricants, etc., should be employed to break up the fibers to restore flexibility. Also, many thermoplastic materials have relatively high friction coefficients and the lubricants are useful to reduce friction in the sewing step.

The thread used in the process of this invention is conveniently produced by dipping a conventional sewing thread in an organic or aqueous solution of the selected non-fibrous thermoplastic material, followed by squeezing, centrifuging or wiping to obtain the desired solids pickup; and then drying to remove the solvent. Solutions or suspensions of the thcrmoplast can be used. The

lubricant which is preferably present in the sewing thread can be incorporated in these mixtures, if desired, rather than applying the lubricant to the already coated thread. If the selected thermoplastic material is incompletely polymerized, a catalyst can be added to the thermoplast solution or suspension and the coated thread cured to a substantially tack-free state.

As illustrated in the examples hereinafter, a preferred sewing thread is coated with a prepolymer which, when the thread is subjected to the high temperatures employed in the pressing step of the process, polymerizes in situ to form a heat-resistant bond. Materials such as endbloeked polyurethanes, in. polyurethanes having blocked it oeyuuate groups as terminal groups. are well mille r this purpose.

In the sewing step the ends of the textile web are sewn together to form a butt, i.e., nonoverlapping, seam using the usual industrial railroad or other type sewing equipment or the sewing can be conducted by hand.

The textile web at the seam area is then subjected to substantial pressure, i.e., at least 10 pounds per square inch, preferably 25-200 and more preferably 50-100 pounds per square inch, so as to press the exposed portions of the sewing thread firmly into the face of the fabric. The amount of pressure required to do this will depend upon the yieldability of the web and the thickness of the sewing thread. Simple experimentation can readily determine the pressure required. Excessive pressures which cause destructive crushing of the fabric should be avoided. Only that pressure which presses the exposed portions of the sewing thread tightly into the plane of the faces of the web is required.

The fabric is then heated at the seam area while under the pressure described above to at least the flow temperature of the thermoplastic non-fibrous component, preferably at least 25 C. above the flow temperature. However, the temperature to which the textile web is heated at the seam area should be below the temperature which would cause substantial degradation of the web or of the fibrous supporting component, i.e., degradation sutlicient to Weaken the fabric or the thread so that the web ends will part under conventional tensions applied in subsequent processing. As the preferred thermoplastic nonfibrous components have a flow temperature between about and 200 C., more preferably about to 200 C., the web at the scam area will ordinarily be heated to a temperature between about 150 and 225 C. If the fibrous supporting component is also thermoplastic, e.g., nylon or Dacron, somewhat greater care must be exercised to ensure that the web is not heated at the scam area to a temperature which causes substantial loss in strength of the fibrous component. However, if the temperature to which the web is heated does not substantially exceed 225 C., sufficient strength in the thread will be retained to hold the seam together in subsequent operations.

If the means for applying pressure to the seam is a heated platen, which is the preferred apparatus for performing the process of this invention, the heating of and applying pressure to the Web will occur substantially simultaneously. Apparatus of the type shown in US. Patent No. 3,000,434 is suitable for this purpose.

The seam area is heated at the selected temperature for a time sufficient to cause the thermoplastic component to flow through the yarn and into the textile web. This generally requires less than one minute and usually less than 45 seconds, e.g., 2 to 35 seconds, depending in part upon the temperature employed, the flow temperature of the thermoplastic component and the efiiciency of the heating system employed, e.g., diathermic vs. conductive heating. All that is required is that the flow temperature of the thermoplastic component be reached.

The seam is then permitted to cool below the softening temperature of the thermoplastic component. This causes the sewing thread to adhere tightly to the face of the fabric by the adhesion of the thermoplastic comrotary press.

ponent to the fabric. The pressure is, of course, also removed, either before, at the same time or after the heating means is removed from the seam.

The following examples are illustrative of the processes and products of this invention but are not to be construed as limiting. Unless otherwise indicated proportions and percentages are on a weight basis.

PREPARATION I Pad conventional 4-ply 305 cotton sewing thread with catalyst-containing 35% polyurethane emulsion in water (Thiokol D-424JL) to obtain a 30% solids pick-up, calculated on the dry thread. Dry the thread below 100 C. Apply waxes and/or lubricating coning oils to facilitatc sewing.

PREPARATION II Follow the procedure of Preparation I using a 70% polyurethane latex in sol-vent system (Unithane 500), providing about the same solids pick-up. Comparable results are obtained.

PREPARATION III Follow the procedure of Preparation I using a solution of a thermoplastic-thermosetting plasticized phenolic resin (Minnesota Mining and Manufacturing Type 583 tape) in acetone, to obtain at least a pick-up of the solution. A convenient procedure involves passing the thread, after dipping into the acetone solution, through an aperture of a size which will remove the excess solution leaving the desired solids pick-up. The pick-up can also be controlled by varying the solids concentration of the acetone or other organic solution. Apply a light penetrating oil to the dry thread while eoning to obtain a tack-free, more flexible thread.

Example I Sew together two ends of a conventional all-wool worsted fabric using a conventional railroad sewing machine to form a narrow butt seam, using as sewing thread a thread as described in Preparation 1. Using a platen about 1.5 inches wide and about 72 inches long, heated to about 200 C. :4 C., press the sewing thread tightly into the face of the fabric with about 70-80 lbs/sq. in. pressure. Apply the heat and pressure for about seconds. Raise the platen so as to permit the seam to cool. The resulting scam presents no portions of the sewing thread raised above the face of the fabric. Consequently, the fabric can be passed through a shearing operation without raising the blade at the sea-m area or cutting the sewing threads to any significant extent. The adhesion of the threads on the face of the fabric is excellent so that the fabric can pass through a heated rotary press without releasing the threads from the face of the fabric or causing the fabric or treated thread to stick to the Example 11 Follow the procedure of Example I, using a sewing thread as described in Preparation II. Press for seconds. Adhesion is good. No raised portions of the sewing thread are apparent on either face of the fabric.

Any, some or all of the following variations can be incorporated into the procedures of Examples I and II:

(a) The proportion of polyurethane to cotton in the sewing thread can be varied from 5:95 to 40:60.

(b) The platen temperature can be varied from 190 to 225 C. and the heating time varied, inversely to the change in temperature, from 10 to 120 seconds.

(c) The pressure can be varied from 25 to 200 lbs./

sq. m.

(d) The substrate fabric can be ethylene glycol terephtha'lic acid polyester, polya-crylic, nylon, cotton, rayon, blends of any of these with wool, or blends of any two or more of these.

(c) The polyurethane in the thread can be replaced by any other polyurethane or other polymer which cures to a substantially tack-free state when heated to about 200 C.

(f) The cotton in the thread can be replaced by rayon, nylon, ethylene glycol terephthalic acid polyester or polyacrylic in staple, monofilament or multifilament form.

Example III Follow the procedure of Example I using a sewing thread as described in Preparation Ill. Bond at about 196 C. for about 35 seconds. Cool and release the pressure. The finished seam displays no portions raised above the face of the, fabric and adhesion is excellent. The bonding material becomes thcrmoset under these conditions and no longer will soften at 200 C. or even higher temperatures. Adhesion is excellent.

What is claimed is:

1. A method of joining together the ends of lengths of textile webs so as to provide a seam with a surface that is substantially level with the textile webs which comprises the steps of (1) sewing the ends of the webs together to form a butt seam with a bicomponent sewing thread comprising (a) at least 60% of a fibrous supporting component which neither flows nor substantially degrades when heated for up to about one minute to up to 225 C., at least some of whose fibers are coated with (b) at least 1% of a thermoplastic non-fibrous component providing a coating for the supporting component and having a flow temperature, between about and 225 C., which is below the temperature at which the web substantially degrades when heated for about one minute; and

(2) applying sufiicient pressure to the seam to press the raised portions of the thread in the seam tightly into the face of the web;

(3) applying sufiieient heat, while the seam is under pressure, so as to heat the web at the seam position to at least the flow temperature of the thermoplastic non-fibrous component but below the degradation temperatures of both the web and the supporting component, for a period of time suificicnt to permit the thermoplastic non-fibrous component to flow; and

(4) cooling the seam and releasing the pressure therefrom.

2. A method according to claim 1 wherein the fibrous supporting component is a nonther'moplastic eellulosic tutorial.

3. A method according to claim 1 wherein the nonfibrous thermoplastic component is polyurethane.

4. A method according to claim 1 wherein the fibrous supporting component is cotton.

5. A method according to claim 1 wherein the web is woven fabric.

6. A method according to claim 5 wherein the fabric comprises wool.

7. A method of joining together the ends of lengths of woven fabric comprising wool so as to permit the joined ends to pass through a shearing operation without interrupting the shearing at the seam area which comprises the steps of (1) sewing the ends of the fabric together to form a butt seam with a sewing thread consisting essentially of (a) from 60 to 99% of a nonthermoplastic fibrous supporting component which does not substantially degrade when heated to up to 225 C. for up to about one minute; and

(b) from 40 to 1% of a thermoplastic non-fibrous component having a flow temperature between about and 200 C. and in the form of a coating for the supporting component;

(2) applying sumcient pressure to the seam to press the raised portions of the sewing thread in the seam tightly into the face of the fabric;

(3) applying suilicient heat, while the seam is under pressure, so as to heat the fabric at the seam area to a temperature from at least 25 C. above the flow temperature of the thermoplastic non-fibrous component to 225 C., for a time suificient to permit the thermoplastic non-fibrous component to flow; and

(4) cooling the scam area.

8. A method according to claim 7 wherein the thermoplastic non-fibrous component is polyurethane.

9. A method according to claim '7 wherein the nonthermoptastle fibrous supporti con-i ient is a eel= lulosic.

it). A method according to claim 7 wherein the thermoplastic first fibrous component is polyurethane and the nonthermoplastie fibrous supporting component is cotton.

11. A method according to claim 1 wherein the fibrous supporting component is a thermoplastic material.

8 12. A method according to claim 1 wherein at least one of the textile webs comprises a thermoplastic material.

13. A method according to claim 1 wherein the nonfibrous thermoplastic component is thermosetting upon the application of heat.

References Cited by the Examiner UNITED STATES PATENTS 2,592,463 4/1952 Phillips 156-91 2,714,758 8/1955 Woodson 112403 3,102,835 9/1963 White 117-14O XR FOREIGN PATENTS 514,934 7/1955 Canada.

ALEXANDER WYMAN, Primary Examiner.

JACOB STEINBERG, Examiner. 

1. A METHOD OF JOINING TOGETHER THE ENDS OF LENGTHS OF TEXTILE WEBS SO AS TO PROVIDE A SEAM WITH A SURFACE THAT IS SUBSTANTIALLY LEVEL WITH THE TEXTILE WEBS WHICH COMPRISES THE STEPS OF (1) SEWING THE ENDS OF THE WEBS TOGETHER TO FORM A BUTT SEAM WITH A BICOMPONENT SEWING THREAD COMPRISING (A) AT LEAST 60% OF A FIBROUS SUPPORTING COMPONENT WHICH NEITHER FLOWS NOR SUBSTANTIALLY DEGRADES WHEN HEATED FOR UP TO ABOUT ONE MINUTE TO UP TO 225*C., AT LEAST SOME OF WHOSE FIBERS ARE COATED WITH (B) AT LEAST 1% OF A THERMOPLASTIC NON-FIBROUS COMPONENT PROVIDING A COATING FOR THE SUPPORTING COMPONENT AND HAVING A FLOW TEMPERATURE, BETWEEN ABOUT 100* AND 225*C., WHICH IS BELOW THE TEMPERATURE AT WHICH THE WEB SUBSTANTIALLY DEGRADES WHEN HEATED FOR ABOUT ONE MINUTE; AND (2) APPLYING SUFFICIENT PRESSURE TO THE SEAM TO PRESS THE RAISED PORTIONS OF THE THREAD IN THE SEAM TIGHTLY INTO THE FACE OF THE WEB; (3) APPLYING SUFFICIENT HEAT, WHILE THE SEAM IS UNDER PRESSURE, SO AS TO HEAT THE WEB AT THE SEAM POSITION TO AT LEAST THE FLOW TEMPERATURE OF THE THERMOPLASTIC NON-FIBROUS COMPONENT BUT BELOW THE DEGRADATION TEMPERATURES OF BOTH THE WEB AND THE SUPPORTING 